One kidney in baby?
The 2nd trim. Sono doesn't usually look at maternal structures, so i assume you are talking about the baby having only one kidney.
You need a referral to a maternal-fetal medicine specialist for a level 2 sono; it would be unusual for a good sonographer to miss a kidney if it were there. Ur baby may have only one kidney, which shouldn't indicate genetic disorders and baby should likely b o/w health.